Experimental modal analysis of a rotating rotor
Pathak, Hari (2021)
Diplomityö
Pathak, Hari
2021
School of Energy Systems, Konetekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2021120759230
https://urn.fi/URN:NBN:fi-fe2021120759230
Tiivistelmä
Rotordynamics analysis of a rotating machine is a fundamental process to understand the vibration characteristics of a rotating components as it ensures the proper functioning of the machine. Improper vibration in the machine may cause excessive noise, or even damage the components in the rotating machines. For smooth operation of the rotor system in machines have been studied through Finite element method (FEM), experimental modal analysis (EMA) and operational modal analysis (OMA) over the years.
EMA of rotating machines is a method for obtaining the natural frequencies, mode shapes and damping ratios to evaluate critical speeds and resonances from the measurement. EMA for stationary rotors have been established to some accuracy in the past, however, for rotating rotor case, the modal parameters like frequencies, mode shapes and damping ratios are difficult to extract from the measurement. The reason for this difficulty is the rotating machines having additional lateral and tangential forces along with gyroscopic moments in rotating components. The objectives of this thesis were to obtain the modal parameters of rotating rotor.
The frequencies, mode shapes and damping ratio were established through measurement. In this study the experimental modal analysis is done on the laboratory setup. The main frequencies are compared with for the rotor at stand still and rotating rotor. The measurement was done with 1) accelerometer sensor and impact hammer and 2) scanning vibrometer with automated hammer. Damping ratio was calculated using half power method. The results were compared and found that the obtained modes and frequencies agreed in both cases of measurement to each other.
EMA of rotating machines is a method for obtaining the natural frequencies, mode shapes and damping ratios to evaluate critical speeds and resonances from the measurement. EMA for stationary rotors have been established to some accuracy in the past, however, for rotating rotor case, the modal parameters like frequencies, mode shapes and damping ratios are difficult to extract from the measurement. The reason for this difficulty is the rotating machines having additional lateral and tangential forces along with gyroscopic moments in rotating components. The objectives of this thesis were to obtain the modal parameters of rotating rotor.
The frequencies, mode shapes and damping ratio were established through measurement. In this study the experimental modal analysis is done on the laboratory setup. The main frequencies are compared with for the rotor at stand still and rotating rotor. The measurement was done with 1) accelerometer sensor and impact hammer and 2) scanning vibrometer with automated hammer. Damping ratio was calculated using half power method. The results were compared and found that the obtained modes and frequencies agreed in both cases of measurement to each other.